The present invention relates to a liquid crystal display device which is arranged to display data, and more particularly to the liquid crystal display device which includes pixels disposed in a matrix format.
As the prior arts, the JP-A-9-258168 and the JP-A-11-2797 disclose the liquid crystal display device which includes memory means for holding data on each pixel and switching means for controlling a switching operation according to the data held in the memory means so that an ac waveform may be applied onto the opposed electrode.
For example, in the case of displaying a still picture, these prior arts do not need to enter data during the time when the memory means holds the data and to change a voltage to be applied onto scan lines and data lines. On the other hands, these prior arts implement alternating in asynchronous to the input of the data to be displayed.
These prior arts, however, have a disadvantage that the wires for the display data to be connected with pixels are increased in number as the amount of tone information contained in the display data is increased, resulting in making the overall circuit complicated. For example, if the display data includes 2-tone (21) data per one pixel, only one wire is required for one pixel, while if the display data includes 64-tone (26) data, the number of wires required for one pixel is as many as six.
It is an object of the present invention to provide a liquid crystal display device which enables to display data having a great amount of tone information and may have a simplified circuit arrangement.
It is a further object of the present invention to provide a liquid crystal display device which is arranged to suppress power consumption.
According to an aspect of the invention, the liquid crystal display device includes a liquid crystal panel having a plurality of pixels disposed in a matrix format, a Y-selecting signal generating unit for selecting rows of the pixels, an X-selecting signal generating unit for selecting columns of the pixels, and a tone signal generating unit for generating a tone signal for applying a tone voltage corresponding to the tone information of the display data to each of the pixels.
According to another aspect of the invention, the liquid crystal display device includes a liquid crystal panel having a plurality of pixels disposed in a matrix format, a Y-selecting signal generating unit for selecting rows of the pixels, and a tone signal generating unit for generating a tone signal corresponding to the tone information of the display data, for the pixels specified by the Y-selecting signal sent from the Y-selecting signal generating unit and then supplying the tone signal to the specified pixels. More preferably, the liquid crystal display device is arranged to generate a tone signal corresponding to the tone information of the display data, for each of the pixels disposed on the liquid crystal panel and applying a tone voltage corresponding to the tone signal to the pixels selected by at least one of the Y-selecting signal for selecting the rows of the pixels and the X-selecting signal for selecting the columns of the pixels.
According to another aspect of the invention, the liquid crystal display device includes a pair of substrates at least one of which is transparent, a liquid crystal layer formed between the pair of substrates, a liquid crystal panel having a plurality of pixels disposed in a matrix format and serving to change a transmissivity of the liquid crystal layer, a Y-selecting signal generating unit for selecting rows of the pixels, an X-selecting signal generating unit for selecting columns of the pixels, a tone signal generating unit for generating a tone signal corresponding to tone information of the display data and supplying the tone signal to each of the pixels, a memory circuit for starting to hold the tone signal sent from the tone signal generating unit if the Y-selecting signal sent from the Y-selecting signal generating unit and the X-selecting signal sent from the X-selecting signal generating unit are changed from a non-selecting state into a selecting state, a pulse width modulating circuit for modulating the tone signal sent from the memory circuit in time, for generating a binary pulse width signal, a switching circuit for switching an ac signal into a sensor voltage signal or vice versa according to the level of the binary pulse width signal, and a pixel electrode connected to the switching circuit. More preferably, the liquid crystal display device is arranged to generate the tone signal corresponding to the tone information of the display data, for each of the pixels disposed on the liquid crystal panel, hold the tone signal in the memory circuit provided for each of the pixels if any pixel located on the liquid crystal panel is changed from the non-selecting state into the selecting state, modulate the tone signal sent from the memory circuit in time, for generating a binary pulse width signal, and switch the ac signal into a center voltage signal or vice versa according to the level of the binary pulse width signal and supply the signal into the pixel electrode.
According to another aspect of the invention, the liquid crystal display device includes a liquid crystal panel having a plurality of pixels disposed in a matrix format, a holding circuit provided for each of the pixels and for holding a tone voltage corresponding to the tone information of the display data, a refresh circuit for refreshing the tone voltage held in the holding circuit, and a rewriting circuit for rewriting the tone voltage held in the holding circuit according to the tone information. More preferably, the liquid crystal display device is arranged to hold the tone voltage corresponding to the tone information of the display data in the holding circuit provided for each of the pixels located on the liquid crystal panel, display the data by applying the held tone voltage onto each of the pixels, and select the refresh or the rewrite of the holding circuit according to the tone information.